The disclosed inventions relate to surgical ports and associated dilators. In particular, the inventions relate to surgical ports and dilators useful for minimally invasive surgery.
In the past, surgery typically required large incisions to provide visual and instrument access to the surgical site. These large incisions resulted in significant blood loss, damage to muscle tissue, long healing times accompanied by prolonged pain, and significant scarring. Today, however, many surgeries are conducted using minimally invasive techniques. These techniques minimize patient trauma by creating a relatively small incision, followed by the introduction of dilators to increase the effective size of the incision. Following dilation, surgery is performed through a surgical port inserted into the dilated incision. Instead of cutting through the muscle surrounding the surgical site, dilation effectively splits the muscle. Splitting, rather than cutting the muscle causes less damage to the muscle and leads to faster recovery times and reduced patient discomfort.
Dilators develop a channel from the subcutaneous layer of a patient to the site of operation. A small incision, paralleling any underlying muscle, is made slightly longer than ½ the circumference of the largest dilator, or if used, port. A solid, pointed rod, variously described as a first dilator or guidewire, is then inserted into the incision to penetrate the underlying structures and reach the surgical site. It is best if the rod can be positioned against a bony surface as application of the dilators will attempt to push this rod forward. X-rays may be taken before and/or after insertion of the rod to confirm placement at the desired surgical site.
Increasingly larger diameter dilators can then be sequentially placed over each other to enlarge the channel. The larger diameter of the sequential dilators help to dilate the path of exposure while the series of tubes lessens the forces needed to create the path. The pointed tip of the dilators eases insertion and helps to widen the base of the channel when the dilator is orbited around a central axis formed through the center of the dilator along its length at the level of the skin.
In lieu of dilation, mechanical retractors can be used. Mechanical surgical retractors are hand-held or table-mounted metal retractor blades that are inserted into the incision, and thereafter retracted and held or locked in place to increase the effective opening of the incision. A drawback of using retractors is that, in comparison to dilators, a relatively large incision must be made to provide for placement of the retractor blades. Dilators and surgical ports, on the other hand, typically gain access to the surgical site by making a smaller incision, inserting a small probe into the incision, and then creating a progressively larger circular opening by repeatedly sliding larger dilators over the probe, thereby splitting the muscle. This splitting of the muscle is less traumatic and therefore offers a quicker post surgery recovery.
Conventional dilators and surgical ports, however, are not suitable for all surgical applications. For example, conventional dilators are unable to completely dilate muscle away from the lamina of the spine due to the tortuous geometry of the lamina. Thus, muscle located between the dilator and the lamina must typically be cut away to access the lamina when using conventional dilators.
Due to the geometry of the spine, many spinal surgical procedures require a long, narrow opening. Thus, another drawback of dilators is that a circular opening is not practical for most spinal surgeries because of the limited access it offers to the spine given the size of the dilated opening. The use of dilators and surgical ports are therefore generally limited to procedures involving very precise access to the spine, such as for single level discectomy.
Mechanical retractors, on the other hand, offer the promise of a long, narrow opening. As discussed above, however, mechanical retractors require a relatively large initial incision that involves cutting, rather than splitting of muscle.
Hence, there is a long-felt need for a device and method for enlarging minimally invasive incision by dilation, regardless of the orientation of the surgical access in relation to the surgical site. There is also a long-felt need for a device and method for enlarging minimally invasive incision by dilation that can displace muscle away from surgical sites possessing a tortuous geometry. Furthermore, there is also a long-felt need for a device and method for enlarging the dilated incision to create a long and narrow access to the surgical site by splitting, rather than cutting muscle surrounding the surgical site.